Beginner Questions (Please review my plan) [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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03-05-2007, 10:27 PM
I am getting ready to tile our kitchen (new construction - no cabinets, just open space), and could use some expert advice/help from you all. Currently there is 3/4" OSB flooring nailed down by the builder and the joists are 16" on center. The kitchen will open up to 3/4" hardwood floors that will be installed after I lay the tile down and will transition in 4 areas. I plan to secure the OSB further with 2" course thread screws.

I plan to lay a supporting bed of Mapei Kerabond with 1/4" trowel under 1/2" Hardibacker (I plan to follow Hardibacker's installation instructions - staggering the Hardibacker over the OSB, leaving 1/8" gaps between boards and 1/4" space at the walls, using their screws, filling and taping the seams, etc). I then plan to lay Mapei Ultracontact as a supporting bed for the tile with a 1/2" trowel and set 400 square feet of DalTile's Paraiso (5/16" thick Glazed Porcelain) in a plain weave pattern that consists of 57% 20"x20" tile, 29% 10"x20", and 14% 10"x10".

Here are my questions:
1. Any recommendations on course thread screws to secure the OSB to the floor joists? How far should they be apart? Is this a good idea or a waste of time/money?
2. Should I install additional plywood (3/8") over the OSB since the majority of my tiles are 20"x20"?
3. Is a 1/2" trowel the right size to use under the tile - again following advise to use a 1/2" trowel under the tile since they are mostly 20x20"?
4. Any other ideas, comments, suggestions are much appreciated - thanks!

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03-05-2007, 10:38 PM
Use deck screws to anchor the osb. The 3/4" might be fine, but you really need to check out the deflecto to check for stability of the floor.

More ply is always nice. To help keep the heights of the floors close, consider using a membrane - it is much easier than putting down cbu. Both Custom, Noble, and Schluter make decent ones. I've only used Ditra, and it was a piece of cake - much easier than humping the cbu.

03-05-2007, 11:07 PM
Dido with Jim, That's a pretty good amount of sq. footage and the extra ply and ditra will certainly help. I don't know that you will gain any more strength going to the 1/2" backer? I think the trowel size is good too!